The typical time pressures encountered by a traveler meeting airplane or train schedules are often complicated by large, cumbersome and/or heavy suitcases or like articles of luggage. In order to avoid the direct lifting or carrying of such luggage, individual articles of luggage are characteristically rendered movable along an underlying ground or support surface by the provision of a number of wheels or castors attached to the bottom surface or wall of the luggage for rotation in the forward direction of travel. In some cases, such wheels are implemented as castors which are capable of pivoting about an axis defined substantially perpendicular to the bottom wall, thereby facilitating changes or variations in the intended direction of forward movement of the luggage along the support surface. Each piece of movable luggage also typically possesses a strap or other handle connected to or proximate the top wall or surface or along a side or front face thereof for permitting the user to pull the luggage along the ground surface and/or carry the luggage from place-to-place.
The pull-forces necessary for causing such wheeled luggage to move from a rest position to a moving state along the ground surface, or for changing the direction of motion while the luggage is in the moving state, are thus generally directed to a point located at or above, and most typically substantially higher than, the center of gravity of the luggage. As a consequence, the required pull-forces to move such articles of luggage can easily result in unintended tipping or misdirection of the article on or along the underlying support surface. Turning or redirection of the luggage from a stopped position or while the article is in motion further requires that the user overcome the then-current inertial forces by pulling, pushing or twisting the handle or strap so as to translate and distribute the turning forces through the luggage to the pivotal axes of the wheels or castors. It is only in this manner that the wheels are turned via such translated forces to change the direction of travel. It can therefore be appreciated that greater forces are required to turn such an article of wheeled luggage than to simply move the article forwardly along a straight line, since a rather sizeable component of the forces exerted must first turn the entire mass of the article to rotate the attached wheels, leaving only the remaining force component for actually advancing the article in its intended new direction. Moreover, the handle or strap attached to the luggage, through which these forces are applied and distributed, is severely stressed by such ations, and a potentia point of component failure is established at the attachment of the handle. Additionally, changing the direction of motion of the luggage is frequently a slow, difficult and imprecise process as a consequence of the need to pull, push or twist the handle in order to successfully translate these forces from a twisting action of the mass or weight of the luggage to a pivoting action of the wheels or castors about their pivotal axes. Such known devices are therefore intrinsically restricted in their freedom of motion by virtue of their design and are relatively ineffective and inefficient in energy-input requirements and in their capacity to suitably distribute the forces for motion. Although there have been numerous attempts to provide an assembly which overcomes the above-mentioned drawbacks, the proposed devices or arrangements are typically unacceptably expensive or complex to manufacture and often add undue extra weight to the article of luggage.
Castors for container supports, in contrast to those provided for moving luggage along a flat surface, have long been known in the art. For example, in U.S. Pat. No. 1,975,291 to Ritter, Jr., a series of castors provides rotary support of a trunk having oppositely-disposed luggage compartments to enable manipulation of the closure of the trunk without requiring a shift or change in position by the operator. However, the Ritter castors are neither utilized nor suggested for use in moving the luggage along a flat surface.
As shown in U.S. Pat. No. 2,605,989 to Luft, roller assemblies have been used as a turntable base for moving luggage along a flat surface or floor and for providing pivoting of the piece of luggage upon the assembly to which it is attached. However, for the same reasons noted above, Luft's rolling assemblies are restricted in their freedom of motion and are inadequate in their distribution of the forces for moving the luggage and changing its direction of motion.
The use of castor mountings for luggage is also known in the art. For example, in U.S. Pat. No. 3,526,921 to Aupke, castors are provided along a bottom face of a suitcase and are removably mounted through socket apertures drilled or punched in the bottom face. Aupke's castors possess the drawbacks described above, i.e. pivoting is imprecise and difficult, and the forces required for moving the suitcase are input at a location that lies a substantial distance above the center of gravity, rather than directly to a pivoting point. Consequently, freedom of motion of Aupke's luggage is restricted, and the forces must be distributed through the handle which, in Aupke's device, is the same top-wall handle that is used for carrying the luggage.
A luggage handle doubling for both carrying and moving, along an underlying surface, a piece of wheeled luggage is also disclosed in U.S. Pat. No. 4,838,396 to Krenzel. The Krenzel luggage handle enables the user to maintain a relatively upright position while dragging the case along a ground surface. The rear face of the Krenzel luggage carries a single front castor wheel and non-pivoting rear wheels, i.e., wheels which do not pivot about an axis defined substantially perpendicular to the rear face of the luggage. Such wheeled luggage possesses the same drawbacks pointed out above and, in addition, the single front wheel of this particular arrangement provides seriously diminished stability in maintaining the luggage in an upright condition as it is moved along an underlying support surface.
A removable luggage carrier is also described in U.S. Pat. No. 3,861,703 to Gould in which each of four separate castor wheels is mounted on a plate that is attached by releaseable fasteners to a side or rear face of and proximate a respective corner of an article of luggage. The luggage handle normally used for carrying the article equipped with the Gould device is also employed for moving the luggage along a flat surface upon the detachable castor assemblies. Thus, Gould neither addresses nor overcomes the problems discussed above.
The present inventor's co-pending U.S. patent application 07/725,339 describes a moveable article of luggage having a pair of freely-rotatable front wheels mounted to a retaining and pivoting assembly which maintains the front wheels at a fixed distance apart, and a pull-type handle device. The retaining and pivoting assembly provides for unitary and concurrent pivoting of the front wheels about a forward axis and is pivotally secured to the bottom wall of the luggage article at the forward axis. The handle device is, in turn, attached to the retaining and pivoting assembly for distributing and translating the forces required for moving the luggage along an underlying support surface and for changing the direction of rolling travel of the luggage by accurately pivoting the retaining and pivoting assembly in a direct and unitary manner. Such an arrangement, although successfully overcoming the most significant of the deficiencies of the prior art, is of relatively complex construction and may, depending upon the materials used in fabrication and construction, undesirably add unnecessary weight to the resulting article of luggage.